The microfacies of the Upper Cretaceous carbonates from Ghardaïa region (Algerian north Sahara).

Abstract

The Upper Cretaceous carbonate platforms of the Ghardaïa region (northern Algerian Sahara) record critical paleoenvironmental shifts associated with the Upper cretaceous transition. This study presents a detailed sedimentological and paleoenvironmental analysis of three key stratigraphic sections: Mansoura, Oued Nachou, and Berriane. A primary challenge in interpreting this region is the intense, pervasive dolomitization that frequently obscures original sedimentary textures and biological assemblages. Therefore, the main objectives of this research are to conduct reliable paleoenvironmental reconstructions using surviving microfossil and microfacies assemblages. Through integrated lithostratigraphic logging, analysis of washed residues, and carbonate petrography, including the detailed examination of thin sections to characterize microfacies and diagenetic features, this study tracks the evolution of the platform from restricted argillaceous-evaporitic environments to open-marine carbonate build-ups. Ultimately, this work seeks to clarify the local sedimentary signature of the global Cenomanian-Turonian marine transgression within the heavily diagenetically altered Chebka du M’zab.